1. Field of the Invention
The present invention relates to an image processing apparatus for processing image data read by an image reading apparatus. More specifically, the invention relates to an image processing apparatus capable of carrying out high speed processing, the apparatus being preferably used in a digital photoprinter and the like which continuously outputs finished prints by continuously reading original images.
2. Description of the Related Art
At present, an image recorded on a photographic film such as a negative film, a reversal film and the like (hereinafter referred to as a film) is printed to a photosensitive material such as a photographic paper and the like by so-called direct exposure which subjects the photosensitive material to conventional areal exposure by projecting an image recorded on a film.
Recently, printers using digital exposure (i.e., digital photoprinters) have been developed and put to practical use. In the digital photoprinters, after image information which has been recorded on a film is photoelectrically read out, the read-out image information is converted as digital image data to be recorded by being subjected to various kinds of image processing. Then, a photosensitive material is scanned with and exposed to recording light modulated in accordance with the image data to thereby record an image (a latent image). The recorded image is developed and a resultant photographic print is obtained.
In the digital photoprinters, since a film is photoelectrically read out and exposure conditions are determined after a color/density correction is performed by signal processing, the period of time during which a single image is exposed is short and the exposure time is fixed with respect to image size. As a result, printing can be carried out faster as compared with the conventional areal exposure.
Editing such as combining of a plurality of images, division of an image and the like, and image processing such as color/density adjustment and the like, can be carried out freely. Therefore, finished prints edited and processed freely in accordance with their use can be output. Since the recorded images on finished prints can be stored in a recording medium such as a MO (magneto optical recording medium) and the like as image data, it is not necessary to prepare a film serving as an original image to make additional prints. Further, since it is not necessary to determine exposure conditions again, a job can be promptly and simply carried out.
In prints made by conventional direct exposure, the images recorded on film cannot be perfectly reproduced to resolution, color/density reproducibility and the like. However, with digital photoprinters, recorded prints can be reproduced and output with near perfect accuracy.
Basically, the digital photoprinters comprise an image reading apparatus (scanner), an image processing apparatus (image processor), and an image recording apparatus (printer).
In the scanner, reading light produced by a light source impinges upon a film to thereby obtain the projected light which carries an image recorded on the film. The image carried by the projected light is formed on an image sensor such as a CCD (charge coupled device) sensor or the like through an image forming lens, and read out by subjecting the projected light to photoelectrical conversion in the image sensor. Then, after various kinds of necessary image processing, the image is input to the image processing apparatus as image data (information) on a film.
The image processing apparatus sets image processing conditions in accordance with the image data having been transferred from the scanner and displays an image which was processed in accordance with previously set conditions. After the operator carries out testing and adjusts the image processing conditions, the image data are subjected to a determined image processing and input to the printer as output image data (exposure conditions) for recording the image.
Where the printer is an apparatus which makes use of a light beam scanning exposure, light beams are modulated in accordance with the image data input from the image processing apparatus and deflected in a main scanning direction. Also, the photosensitive material (photographic paper) is conveyed in an auxiliary scanning direction, which is normal to the main scanning direction. In this manner, the photosensitive material is two-dimensionally exposed to (or printed by) the light beams carrying an image to thereby form a latent image. The photosensitive material is then subjected to development processing in accordance with the photosensitive material. Finally, a finished print (photograph) is thereby obtained.
In this digital photoprinter, the images in the respective frames are continuously read frame by frame with a scanner. The read-out image data is then sequentially transferred to an image processing apparatus and subjected to image processing, and processed image data is then sequentially transferred to a printer and continuously exposed in the sequence it is transferred.
Therefore, in order to realize high productivity, it is preferable that the scanner, image processing apparatus and printer operate at all times and continuously carry out processings without interfering with other units.
For this purpose, the image processing apparatus for the digital photoprinter requires a sufficient processing speed such that the reading of the image by the scanner and the recording of the image by the printer are not stopped. Specifically, the digital photoprinter requires a processing speed which is high enough so that the transfer of the image data from the scanner to the image processing apparatus is not delayed, and so that the printer need not wait for the transfer of the image data from the image processing apparatus. In summary, a higher processing speed is required for the image processing apparatus.